1. Field of the Invention
The present invention relates to air pressure controls used in the agricultural field, and, more particularly, to an air pressure control system used on planters.
2. Description of the Related Art
Agricultural planters are commonly used implements to plant seeds in soil. An agricultural planter can include a chassis that carries one or more storage tanks carrying seed, and chemical applications that are to be applied to the field during the planting operation, a hitch mechanism that attaches to a tractor or other implement pulled by a tractor, and a tool bar that row units can be connected to so they are carried by the chassis. The planter can also include a pneumatic system carried by the chassis that supplies pressurized air to transport the seeds or other particulate from the storage tanks to the row units.
Each row unit of the agricultural planter independently places seeds in the field. Typically, the row units are laterally arranged along a length of the tool bar so that as the planter is pulled across the field, each row unit plants seeds at predefined intervals along the path it is pulled across. To plant seeds, the row units perform four main operations as they are pulled: opening a trench in the soil; placing a seed into the formed trench at appropriate intervals; closing the formed trench to put soil on top of the placed seed; and packing soil on top of the seed to provide desirable soil contact with the placed seed. To open a trench in the soil, a furrowing disc system, also called an opening disc, cuts into the soil and rotates, dislocating soil as it rotates to form the trench. Once the trench is open, a seed is placed in the trench by a metering device which receives seeds from the main storage tank(s) or a row unit storage tank and typically utilizes a combination of differential air pressure, to select the seed, and gravity to place the seed in the trench at predefined intervals along the pulled path so that adjacent seeds in the row are not too close to one another. One or more closing discs carried behind the furrowing disc are pressed into the soil and also rotate as the planter is pulled to replace soil dislocated by the furrowing disc in the trench or dislocate adjacent soil into the trench to cover the seed placed in the trench with soil. Finally, a pressing wheel carried behind the closing disc(s) exerts pressure on the soil covering the seed to press the soil down onto the seed and provide good soil contact with the seed. By having multiple row units working in unison as the planter is pulled across a field, many seeds can be effectively planted in an efficient manner.
The vacuum fan has a key roll in the apparatus used for planting seeds in a field. Among other possible functions, it is used to create a pressure differential within a series of seed metering devices, which results in seeds adhering onto a metering disk so that they may be accurately and consistently delivered through the planter mechanism to the soil. The fan for this purpose typically has a high flow rate owing to the number of planter components. In the arrangement of the planter, the fan is coupled to the planter that is behind the operator of a tractor used to pull or support the planting apparatus. The inlet or suction side of the fan is connected to the seed metering mechanisms. The rotational speed of the fan is set by a selection of the operator and is generally in the 3,000 to 5,000 RPM range, depending upon the capacity of the fan and the number of row units connected. The speed of the fan or vacuum level, having been selected, is maintained during the planting operation until the set point is reselected by the operator.
A problem with the prior art is that the fan speed or the vacuum level selected by the operator is not altered even though the planter changes operating speeds and executes turns. Another problem is that the force required to transition a seed from a stationary position to a dynamic position increases as the velocity of the metering device increases, proportional to the travel speed, and conversely as the travel speed decreases and this is not compensated for in the prior art.
Accordingly, what is needed in the art is a vacuum fan that is responsive to changes in the operating conditions of the planter.